Recently, 2Tx antennas have been introduced into WCDMA (Wideband Code Division Multiple Access) and HSPA (High Speed Packet Access) networks in order to support MIMO (Multiple-Input Multiple-Output) transmissions.
WO2006/071153 presents one known way to implement 2Tx MIMO. It is disclosed, an antenna device for a radio base station in a cellular telephony system, which comprises a first and a second input connection for a first and a second data stream, and a first and a second polarization former, one for each of said data streams. The device also comprises a first and a second antenna of respective first and second polarizations, and one amplifier each. The device also comprises a first and a second combiner, so that the outputs from the polarization formers may be combined as input to each of the first and second antennas.
4-layer MIMO transmission in HSDPA has been proposed. However, no feasible solution for how this is solved in a transmission antenna is presented in the prior art. In particular, there is no known solution of how to provide support for one, two and four layers, while providing good sector coverage and power distribution between antennas for all these scenarios.